The present invention relates to a lamp lens, and particularly to an exterior vehicle lamp lens such as an automotive headlamp lens. A method for fabricating such a lamp lens, and a lamp which includes such a lamp lens, is also disclosed.
The lamp lens of the present invention is illustrated herein with reference to an automotive headlamp lens. However, it will be apparent to those skilled in the art that the lamp lens of the present invention is not limited to such an application.
The use of automotive headlamps in the form referred to in the art as a glass sealed beam is well known. In use, such lamps are subjected to intense environmental conditions which tend to lower the overall performance and longevity of the lamps. For example, it is not uncommon for the outer surface of such lamps to be eroded during use by road grit, sand, stones and the like. Various efforts have been made to overcome such problems. In 1995, the National Highway Traffic Safety Administration permitted the use of replaceable headlamp lenses. Since then, replaceable lamp lenses have been commercialized in some applications to replace the conventional glass sealed beams. For example, in the heavy truck industry lamps having plastic lenses are beginning to replace glass sealed beams. One replaceable lens which has been particularly satisfactory is a polycarbonate lens.
The use of a replaceable polycarbonate lens provides one solution to the problem of deterioration in lighting performance caused by environmental conditions. However, such solution has not been without concern regarding cost. For example, the typical replaceable plastic lens requires that the headlamp design incorporate a gasket with lens clips rather than a simpler and less expensive adhesive seal. This has been a particular concern in the heavy truck industry where lens replacement tends to be more frequent.
Efforts have been made to reduce the frequency of lens replacement by providing a more durable lens. For example, it is known to provide the typical polycarbonate lens with a hard coating to protect the lens from environmental damage. Heretofore, such attempts have been compromised due to the inconsistent requirements that the coating be sufficiently soft to absorb impact and sufficiently hard to provide hard abrasion resistance properties to prevent marring. As a result of this compromise, materials presently in use must balance such properties to meet both requirements, and such balancing tends to lower the overall performance.
The demand in the industry for better performance and longevity of lamp lenses has intensified. Customers of headlamp manufacturers are presently requesting that headlamps perform satisfactorily for 200,000 miles or the life span of the vehicle. However, materials available in the industry for use in fabricating the conventional polycarbonate lamp lenses provide only four or five years weathering performance before reaching the standard specified maximum of 7% haze in the polycarbonate lens. One problem is that although a hard coating generally resists erosion of the lens outer surface caused by grit, sand, stones and other debris from the road surface striking the plastic lens, the coating tends to chip off of the polycarbonate substrate when subjected to heavy impacts. Efforts to provide a softer material provides a lens coating which creates a flexible cushion that permits the surface coating to flex under heavy impacts and thereby resist chipping. However, a soft lens coating quickly erodes or becomes dull. In particular, lenses having soft coatings fail to pass the required conventional (FMVSS-108) steel wool scratch test.
It is an object of the present invention to provide an improved lamp lens. Another object of the present invention is to obviate the disadvantages of the prior art by providing an improved lamp lens.
A further object of the present invention is to provide a lamp lens having improved overall performance and longevity.
It is still another object of the present invention to provide a lamp lens which resists erosion by grit, sand, stones and other debris.
Another object of the present invention is to provide a lamp lens which has sufficient hardness to provide abrasion resistance and sufficient softness to absorb impact of grit, sand, stones and other debris.
Yet another object of the present invention is to provide a lamp lens the surface of which does not become pitted or otherwise chipped.
A further object of the present invention is to provide a lamp lens which provides satisfactory impact resistance and meets a standard steel wool scratch test.
Another object of the present invention is to provide an exterior vehicle lamp which satisfies any one or more of the foregoing objects.
Yet a further object of the present invention is to provide a vehicular headlamp having a lens which satisfies any one or more of the foregoing objects.
Still another object of the present invention is to provide a method for producing a lamp lens which satisfies any one or more of the foregoing objects.
This invention achieves these and other objects by providing a lamp lens which comprises a clear lens base having an inner surface and an opposite outer surface. A flexible first layer is adjacent the outer surface. An abrasion resistant second layer is adhered to the first layer. The first layer is softer than the second layer. A method for producing, and a vehicular headlamp comprising, the lamp lens of the present invention is also provided.